Formaldehyde is a naturally occurring volatile organic compound with the formula CH2O. Formaldehyde is an important precursor in the production of many other materials and chemical compounds, such as particle board and various coatings.
Formaldehyde is toxic and recognized as a carcinogen. The United States National Institute for Occupational Safety and Health (NIOSH) considers 20 ppm formaldehyde in the atmosphere to be immediately dangerous to life and health (IDLH). The United States Occupation Safety and Health Administration has established a permissible exposure limit (PEL) for formaldehyde in the workplace at 0.75 parts formaldehyde per million parts of air (0.75 ppm) measured as an 8-hour time-weighted average (TWA). Other agencies and organizations have recommended that the acceptable level be reduced to less than about 0.10 ppm (100 ppb).
An excellent review of the various formaldehyde gas sensors developed over the years is provided in Chung, P.; Tzeng, C.; Ke, M.; Lee, C., Formaldehyde Gas Sensors: A Review, Sensors, 2013, 13, 4468-4484. Such sensors, while generally effective for measuring formaldehyde concentrations in air, tend to lack the necessary sensitivity and/or are far too expensive for widespread use. Accordingly, a substantial need exists for an economical yet robust and highly sensitive formaldehyde sensor capable of providing a quick response.